Desync
Also called: Desynchronization, Out of sync
A desync is a multiplayer bug where two or more players' game states drift apart, so each client shows a different version of the same match.
Desync means the clients in a multiplayer session no longer agree on what is happening. One player sees an enemy dead, another sees it alive. In lockstep games such as RTS titles, the simulation can split completely and the match ends with an error. In client-server games it shows up as rubber-banding, ghost hits or items that exist for only one player.
On Steam, desync reports tend to arrive in the first days after launch, when real players connect from different regions, with mixed hardware and with packet loss that a studio LAN never produces. Late joins, host migration, save and load in co-op, and reconnecting after a dropped connection are the usual triggers.
QA hunts desync with at least two machines on separate networks, a network condition tool that adds latency and packet loss, and scripted sessions that repeat the same actions. Each report records which client saw what, the timestamps and the session logs from both sides. Without logs from every client, a desync is very hard to fix.
Updated · Written by JJ, founder of Jumbo Jelly.
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Related terms
- Soak test
A soak test runs a game build for many hours without restarting to catch memory leaks, slowdowns and crashes that only appear over long sessions.
- Repro steps
Repro steps are the numbered actions that make a bug happen again on demand, written so a developer can trigger it without asking the tester anything.
- Day-one patch
A day-one patch is an update released on or right after launch day to fix bugs found after the release build was locked or once players arrived.
- Steam beta branch
A Steam beta branch is a separate build of a game that players opt into from the game's properties, often locked with a password for testers.